Notice: Users may be experiencing issues with displaying some pages on stanfordhealthcare.org. We are working closely with our technical teams to resolve the issue as quickly as possible. Thank you for your patience.

What Causes Obesity?

On the surface, the cause of obesity seems simple: if you consume more calories than you burn as energy through physical activity, then you'll gain weight. But like many things, the simple explanation is often incomplete.

The risk factors that contribute to obesity can be a complex combination of genetics, socioeconomic factors, metabolic factors and lifestyle choices, among other things. Some endocrine disorders, diseases and medications can also cause weight to increase.

Common factors influencing obesity

Genetics – Studies have shown that you can inherit a tendency toward obesity. Your chance of being overweight increases 25 percent if one or both of your parents is obese. Heredity also strongly influences where you carry weight – the hips or around the middle.

Metabolic – How you expend energy differs from how someone else will. Metabolic and hormonal factors are not the same for everyone, but these factors play a role in determining weight gain. Recent studies show that levels of ghrelin, a peptide hormone known to regulate appetite, and other peptides in the stomach, play a role in triggering hunger and giving you a feeling of fullness after eating.

Lifestyle – Overeating in combination with a sedentary lifestyle, contributes to obesity. Changing your behavior can affect these lifestyle choices. If you eat a diet in which a high percentage of calories come from sugary, high-fat, refined foods, chances are you'll gain weight. As more American families eat on the go and people look for low-cost options, more people reach for high-calorie and -fat foods and beverages like fast food.

Couple that with a lack of regular exercise and it becomes very difficult for adults to maintain or lose weight. For children, activities that don't expend energy, such as watching television or sitting at a computer, contribute to obesity.

Clinical Trials

Clinical trials are research studies that evaluate a new medical approach, device, drug, or other treatment. As a Stanford Health Care patient, you may have access to the latest, advanced clinical trials.

Open trials refer to studies currently accepting participants. Closed trials are not currently enrolling, but may open in the future.